SOIL NUTRIENT HETEROGENEITY ALTERS COMPETITION BETWEEN TWO PERENNIAL GRASS SPECIES

Abstract

Differences in root foraging behavior between species have been well documented, but the effects of these differences on belowground competitive ability are only beginning to be studied. Here we report the results of a competition experiment in homogeneous and heterogeneous soils between two species that differ in their ability to acquire nutrients from patchy environments. The perennial grasses Festuca rubra and Anthoxanthum odoratum have comparable growth rates, but results of previous studies with isolated plants designated the latter species as the more effective forager, probably due to its higher physiological plasticity (stronger increase in nutrient uptake rates per unit root mass in enriched nutrient patches). We introduced nutrient soil heterogeneity at two spatial scales. In a fine-grained heterogeneous treatment, the nutrient-rich patches were smaller and more concentrated than in a coarse-grained heterogeneous (checkerboard) treatment. Overall, the level of nutrient availability in these hete...